1. Field of the Invention
The present invention relates to a method for producing a single-crystal thin film, and particularly, to a method for producing a single-crystal thin film composed of (BaxSryCaz)TiO3 (wherein x+y+z=1.0), such as barium strontium titanate (BST). Specifically, the present invention relates to a method for producing a single-crystal thin film such as a single-crystal dielectric thin film that can be used as, for example, a substrate for use in a sensor and a dielectric film for use in a capacitor, a single-crystal conductive thin film that can be used for a switch and a contact for use in a display and a touch panel and an electrode of a sensor, and a transparent single-crystal thin film that can be used for an electric field-application type of optical switch for use in a waveguide of an optical communication device.
2. Description of the Related Art
Hitherto, examples of a process for producing a single-crystal dielectric thin film include sputtering, MBE, pulsed laser deposition, and MOCVD. A satisfactory single-crystal dielectric thin film can be produced by the method for producing a single-crystal dielectric thin film of the related art. The single-crystal dielectric thin film usually has high performance.
Japanese Unexamined Patent Application Publication No. 7-133188 discloses a process for forming an epitaxially grown or highly oriented ferroelectric oxide thin film by applying an organometallic compound precursor solution on a single-crystal MgO or MgAl2O4 substrate and annealing the applied solution.
Japanese Unexamined Patent Application Publication No. 2007-180398 discloses a process for forming a BST-based high-dielectric film used for a capacitor such as a decoupling capacitor by, for example, applying a dielectric precursor solution containing titanium, barium, strontium, and lithium on a base to form a film.
However, since the processes for producing a single-crystal dielectric thin film of the related art employs sputtering, MBE, pulsed laser deposition, MOCVD, or the like, those processes requires complex conditions, facilities, and steps. It is thus difficult to produce a single-crystal dielectric thin film without increasing the production cost of the single-crystal dielectric thin film.
Furthermore, since the process for producing a single-crystal dielectric thin film of the related art employs sputtering, MBE, pulsed laser deposition, MOCVD, or the like, the raw materials for a single-crystal dielectric thin film produced are limited, leading to difficulty in adjusting the composition of the produced single-crystal dielectric thin film.
According to the process disclosed in Japanese Unexamined Patent Application Publication No. 7-133188, a Pb-based ferroelectric oxide thin film is formed, but the Publication does not describe a specific process for producing a high-performance barium strontium titanate (BST)-based single-crystal dielectric thin film. Similar to Japanese Unexamined Patent Application Publication No. 7-133188, there are many reports on oriented films of Pb-based complex oxides because of easy orientation of Pb-based complex oxides.
According to the process disclosed in Japanese Unexamined Patent Application Publication No. 2007-180398, a BST-based high-dielectric film is formed but a single-crystal or oriented high-dielectric film is not formed. Japanese Unexamined Patent Application Publication No. 2007-180398 does not describe a specific process for producing a high-performance BST-based single-crystal dielectric thin film.
Accordingly, Japanese Unexamined Patent Application Publication Nos. 7-133188 and 2007-180398 do not describe a specific process for producing a high-performance BST-based single-crystal dielectric thin film. Even if attention is focused on a combination of the processes disclosed in Japanese Unexamined Patent Application Publication Nos. 7-133188 and 2007-180398, it is difficult to produce a high-performance BST-based single-crystal dielectric thin film.
It is thus very difficult to easily produce a high-performance BST-based single-crystal dielectric thin film at low cost and to easily adjust the composition of a BST-based single-crystal dielectric thin film, on the basis of the process of the related art and the processes disclosed in Japanese Unexamined Patent Application Publication Nos. 7-133188 and 2007-180398.